The present invention relates to a device which serves to lower a support with an object suspended thereon into a bath filled with a chemical substance and lifting said support from the bath after the coating process.
Devices of the type under discussion are known. One of such devices has been disclosed in German patent document DE-PS 26 39 542. The lifting device movable up and down is disclosed in this German patent. A relatively short guiding rail having a U-shaped cross-section is pivotally connected to the lifting device. The guiding rail forms, with the aid of the coulisse control during the engagement of the lifting parts of the lifting device in the supporting parts of the object support, a guide for these supporting parts. This conventional device, however, has some disadvantages. As mentioned above, the guiding rail is relatively short so that safety against tilting is obtained only over a relatively short part of the entire downward and upward movement of the object support. It is, however possible in practice in some cases, that an undesired lifting of the lifting parts from the supporting parts, also after the lowering of the object support takes place over such a path that the supports ca be positioned outside the short guiding rail. Then, also possible is the tilting of the object support laterally and thus the damage to the object support, the object itself and further structural components of the device. The coulisse control and the pivoting ability of the guiding rail require a number of bearing places. Inasmuch as these bearing places are positioned at a small distance from the bath containing the most agressive chemicals, these bearing places can be quickly contaminated or chemically attacked.
Should the tilting occur the guiding rail must take the entire tilting weight and transmit it through the bearing places to the lifting device and from the latter further to the transporting carriage. The guiding rail and the lifting device are, however, relatively sensitive and not very stable parts so that difficulties occur when the aforementioned tilting weight should be taken up by them. Furthermore, the conventional lifting device with the guiding rail must carry an approximation switch which in case of disturbance of the lowering and lifting parts would issue a respective signal responsive to such disturbance, and a further lowering of the lifting device would be stopped. This approximation switch is positioned above the bath and can be also damaged by an aggressive vapor or disturbed. In such a case an alert signal would not be issued and the motion of the lifting device would not be ceased, and the object support with the object suspended thereon would tilt to the side until its supporting parts are moved from the relatively short guiding region.
A further disadvantage of the above-described conventional device resides in that the lifting device movable up and down must be provided with movable cables or wires for the approximation switch which can be therefore quickly damaged due to continuous movement. The aforementioned known device also presents a danger of buckling of objects during operation.